Low-migration components, media- or drinking-water carrying works

ABSTRACT

The invention relates to a method for producing components, media- or drinking-water carrying works, in particular fittings, valves, pipes, press connectors, roof or drainage gutters, as well as components for media- or drinking-water carrying works, in particular fittings, valves, pipes, press connectors, roof or drainage gutters. The object to provide a method for producing components for media- or drinking-water carrying works, in particular fittings, valves, pipes, press connectors, roof or drainage gutters, whereby corrosion-resistant components can be produced simply and economically, which components exhibit low migration of metal ions into the medium, for example of lead and nickel ions into drinking water, is achieved in that an ingot or a rod is continuously cast from a copper alloy, wherein the copper alloy has the following alloying components in wt. %: 
 
2%≦Si≦4.5%, 
 
1%≦Zn≦17%, 
 
0.05%≦Mn≦0.6%,
unavoidable accompanying elements to a maximum of 0.5% in total, preferably to a maximum of 0.3% in total, the remainder copper and the ingot or the rod for producing the component is subjected at least to one cold and/or hot forming process.

BACKGROUND

The invention relates to a method for producing components, media- or drinking-water carrying works, in particular fittings, valves, pipes, press connectors, roof or drainage gutters, as well as components for media- or drinking-water carrying works, in particular fittings, valves, pipes, press connectors, roof or drainage gutters.

Metal materials for producing components for media- or drinking-water carrying works, for example, fittings, valves, pipes, press connectors, roof or drainage gutters are subjected to particular requirements, in particular if the works are provided for the supply of drinking water. Firstly, mention should be made of the corrosion resistance of the metal material since the components in contact with the drinking water, for example, should not corrode even after use over many years. At the same time, the metals used should exhibit a low tendency for metal ions to migrate into the medium, i.e. the quantity of metal ions released to the medium should be very low. In drinking water pipes, metal ions hazardous to health, for example, lead or nickel ions, are particularly problematical.

With regard to a simple method for manufacturing corresponding components, the copper alloy used for the components should not only be simple and economical to cast but the components cast therefrom should also be easy to machine mechanically. Since the components are cast and then frequently subjected to mechanical machining, the components should in particular exhibit good machinability. The components produced must also withstand the usual mechanical stresses.

Nowadays, high-copper-containing non-ferrous metal alloys such as bronze or red brass are usually used to produce the media-carrying components of, for example, gas or drinking water pipes. In a conventional red brass alloy, the main alloying components apart from copper are about 1.5 to 11 wt. % tin as well as 1 to 9 wt. % zinc. Lead and nickel can also be present in the lead alloy to improve the machinability. For example, the red brass alloy CuSn5Zn5Pb5 contains between 4 and 6 wt. % tin, zinc and lead with a nickel content of up to 2.0 wt. % and a phosphorus content of up to 0.1 wt. %. This material is distinguished by good castability and a good corrosion resistance. The problem is however, that lead and nickel ions are released from the red brass alloy by migration into the medium, in particular into the drinking water. It is therefore to be expected that in future the lower limits for the release of metal ions, in particular lead and nickel, to drinking water can no longer be adhered to by the red brass alloys which have conventionally been used.

Lead-free components of media-, in particular, drinking-water carrying works are already known from European Patent Application EP-1 045 041, these components consisting of a copper alloy containing up to 79 wt. % copper, 2 to 4 wt. % silicon and the remainder zinc. However, it has been found that the components known from said European Patent Application are capable of being improved with regard to their corrosion resistance.

The known components of media-carrying works consisting of a lead-free copper alloy as well as consisting of red brass alloys used so far also have the disadvantage that these can only be mechanically formed at great expense. For example, cold and/or hot forming is only possible to a very limited extent or not at all. Therefore, the components are usually cast and then machined mechanically to the end product. This results in relatively high costs for the production of corresponding components for media-carrying works since on the one hand the yields in casting method usually used are restricted by the system. On the other hand, the work steps used so far offer little potential for rationalisation or automation.

Starting from this, it is the object of the present invention to provide a method for producing components for media- or drinking-water carrying works, in particular fittings, valves, pipes, press connectors, roof or drainage gutters, as well as components for media- or drinking-water carrying works, in particular fittings, valves, pipes, press connectors, roof or drainage gutters, whereby corrosion-resistant components can be produced simply and economically, which exhibit low migration of metal ions into the medium, for example of lead and nickel ions into the drinking water. In addition, it is the object of the invention to provide corresponding components, in particular fittings, valves, pipes, press connectors, roof or drainage gutters.

The object derived above is achieved according to a first teaching of the present invention by a generic method whereby an ingot or a rod is continuously cast from a copper alloy, wherein the copper alloy has the following alloying components in wt. %: 2%≦Si≦4.5%, 1%≦Zn≦17%, 0.05%≦Mn≦0.6%, unavoidable accompanying elements to a maximum of 0.5% in total, preferably to a maximum of 0.3% in total, the remainder copper and the ingot or the rod for producing the component is subjected at least to one cold and/or hot forming process.

It has surprisingly been found that the components produced according to the invention not only exhibit particularly good migration values and a high corrosion resistance with respect to drinking water but also possess the required mechanical properties for their use in media-carrying works. As a result of the hot and also cold forming, the structure of the components according to the invention is much denser than that of the conventionally produced components which are cast and then machined. This additionally results in an improvement in the migration behaviour as well as the corrosion resistance.

The production costs of the components for media- or drinking-water carrying works can also be effectively lowered by the method according to the invention since the methods used so far, primarily casting and subsequent machining, such as for example, milling, drilling or turning are significantly more costly on account of the low scope for automation and the higher reject rates during casting. Instead of continuous casting, it is naturally also possible to use other possible casting methods for producing the ingot or rod, continuous casting being considered to be the more economical casting method at high production runs.

The silicon content of 2 wt. % to 4.5 wt. % of the copper alloy used according to the invention on the one hand ensures an overall very good migration behaviour, in particular of any lead and nickel impurities which may be present in the copper alloy, into the drinking water. On the other hand, the Si content also influences the mechanical strength of the copper alloy. Firstly, if the Si content is less than 2 wt. %, the migration-inhibiting property of silicon is weakened. At silicon contents higher than 4.5 wt. %, the strength of the copper alloy certainly increases but the ductility of the copper alloy is then too low, particularly in regard to the subsequent mechanical formability.

In order to achieve the required corrosion resistance of the components, the zinc content is limited to a maximum of 15 wt. %. A minimum content of 1 wt. % zinc on the other hand guarantees a minimum machinability of the components if these need to undergo additional machining.

A manganese content of at least 0.05 wt. % improves the structural composition of the components produced according to the invention to give a finer structure and positively influences the solidification behaviour of the copper alloy during casting. The upper limit of 2 wt. % manganese takes into account that manganese also migrates into the drinking water and permissible limits are not exceeded. The fme structure of the copper alloy of the components also brings about improved cold or hot deforming properties of the cast ingot or rods.

The restriction of the impurities to a maximum of 0.5 wt. % in total has the result that the migration of unavoidable alloying components, for example into the drinking water is restricted to the necessary minimum. A further improvement in the migration properties of the components produced with regard to unavoidable accompanying elements of the copper alloy used is achieved by restricting the fraction of unavoidable accompanying element to a maximum of 0.3 wt. % in total.

With reference to the new type of method for producing components of media- or drinking-water carrying works according to the invention, it is also conceivable to add grain-refining materials to the copper alloy used in order to improve the forming properties during the production of the components by means of a finer structure or to reduce fluctuations of mechanical properties in the components produced. The addition of small quantities of boron, for example, 0.001 to 0.5 wt. % can be considered as a grain-refining material. However, other grain-refining materials can also be used to improve the structural composition.

According to a next advantageous embodiment of the method, the copper alloy used additionally has the following fraction of the alloying component zinc in wt. %: 5%≦Zn≦15%.

Since the machinability decreases as a result of a reduction in the Zn content but the formability of the components decreases with increasing Zn content, a Zn content of 5 wt. % to 15 wt. % achieves a good compromise between formability and machinability of the components produced according to the invention. The components produced according to the invention can accordingly not only be subjected to cold and/or hot forming but can also be machined.

A compromise between good strength with adequate elongation values at the same time combined with good migration values of the components produced is achieved according to a next embodiment of the method according to the invention if the copper alloy has the following alloying fraction in wt. % for silicon: 2.8%≦Si≦4%.

According to a next advantageous embodiment of the method according to the invention, a good compromise between fine structure and low migration of manganese components into the drinking water by the components produced according to the invention is achieved by the Mn alloying component having the following fraction in wt. %: 0.2%≦Mn≦0.6%.

Finally the migration of nickel and/or lead lions into the drinking water can be avoided if the copper alloy used according to the invention contains no nickel and/or lead.

On the other hand, the corrosion resistance can be increased if the copper alloy used has a copper content of at least 80%.

If, according to a next embodiment of the method according to the invention, a thick-walled tube or a solid rod is produced from the ingot or the rod using extrusion, semi-finished products for cold and/or hot forming can be provided in a simply manner.

The thick-walled tube is then preferably cold-drawn so that so that this simple method can provide dimensionally accurate tubes with few process steps. As has already been mentioned above, the tube thus produced has a higher structural density than, for example, cast and machined tubes since during the cold forming and also during hot forming, the structure undergoes significant densification and the porosity of the cast structure is reduced.

Starting from this thick-walled tube, it is advantageous according to a further embodiment of the method according to the invention if the cold-drawn tube is formed by an internal high-pressure (IHU) method. By this means, complex low-migration fittings, for example, T-pieces can be produced economically.

If the cold-drawn tube or the IHU-formed tube is subjected in at least one further forming step to bending, expanding, reducing, rolling, thickening, flanging and/or further IHU forming steps with or without intermediate annealing between individual forming steps, more complex components with threads, flanges etc. can also be produced simply.

Thicker-walled components for media- or drinking-water carrying works are then finally produced by at least hot-pressing or die forging in a plurality of steps the thick-walled tubes or solid rods produced by the method according to the invention. During hot-pressing, in contrast to die forging, the component is hot formed in one process step. In die forging the hot forming takes place in several individual process steps. As a result of the good hot formability of the copper alloy used, a considerable increase in the yield of good parts can additionally be achieved in the production compared with the conventional method of casting and subsequent machining.

SUMMARY OF THE INVENTION

According to the invention, after the continuous casting, the ingot is hot- and/or cold-rolled to produce sheets with or without intermediate annealing and the sheets are then subjected to at least one further cold or hot forming step. Thus, hot and/or cold-rolled sheets can be used as initial products to produce fittings, valves, pipes, press connectors, roof or drainage gutters so that considerable potential for rationalisation is opened up during the production of the components. It is also conceivable that the continuous casting can be replaced by other casting methods, for example sand or chill casting, to produce an ingot.

A longitudinally welded tube is preferably produced from the cold- or hot-rolled sheets, which can either be used directly as a component or as a semi-finished product for further forming steps. The longitudinally welded tube produced according to the invention can be longitudinally welded with or without filler material and subjected to further mechanical forming processes, for example, an IHU method, bending, expanding, reducing, rolling, thickening and/or flanging.

If the sheets or the longitudinally welded tube is subjected to deep drawing, end caps, for example, can be produced in a simple manner.

According to a second teaching of the present invention, the object derived above is achieved by components for media- or drinking-water carrying works, in particular fittings, valves, pipes, press connectors, roof or drainage gutters by producing these using the method according to the invention.

As has already been stated, components according to the invention exhibit very little migration of the problematical nickel and lead ions into the drinking water. Furthermore, they can be produced rationally and economically so that the production costs are reduced considerably. Finally, the components produced by the method according to the invention which have undergone at least one hot and/or cold forming step, exhibit a substantially denser structure with a lower porosity as a result of the cold an/or hot forming. This results in an improved corrosion resistance and tightness of the components compared with those produced conventionally by casting and subsequent machining. An improved corrosion resistance at the same time improves the migration vales.

Numerous possibilities exist for configuring and further developing the method according to the invention for producing components for media- or drinking-water carrying works or the components according to the invention for media- or drinking-water carrying works. For this, reference is made to the claims subordinate to claims 1 and 15 and to the description of exemplary embodiments in conjunction with the drawings. The drawings show in

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a diagram presenting a comparison between the quantity of lead ions released into drinking water from components produced according to a first exemplary embodiment of the invention and a conventionally produced component made of a red brass alloy,

FIG. 2 a diagram presenting the quantity of nickel ions released into drinking water from components of the first exemplary embodiment of the invention and the conventional component from FIG. 1,

FIG. 3 a diagram presenting the quantity of copper ions released into drinking water from components of the first exemplary embodiment of the invention and the conventional component from FIG. 1,

FIG. 4 a diagram presenting the quantity of zinc ions released into drinking water in the first exemplary embodiment of the invention and the conventional component from FIG. 1, and

FIG. 5 a to d perspective view of four further exemplary embodiments of components according to the invention for media- or drinking-water carrying works.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the quantity of lead released into the drinking water and its time behaviour. The measurement was made in accordance with the DIN standard DIN 50931-1 over 26 weeks. The DIN standard specifies the test arrangement and the test conditions which can be used to determine the corrosion probability of materials for metal components of a drinking water installation under corrosive loading by drinking water.

The diagram shows the time behaviour of the quantity of lead released to the drinking water from components produced according to a first exemplary embodiment of the method according to the invention, wherein the copper alloy used had the following fractions of alloying components in wt. %:

-   Si: 3.5% -   Zn: 1.6%, -   Mn: 0.5%     unavoidable accompanying elements to a maximum of 0.5% in total, the     remainder being copper.

The components according to the invention, used for the test, in the present case tubes, were produced according to the invention from a continuously extruded thick-walled tube by cold drawing.

The components according to the invention are subsequently designated as components A. The migration values of the components A were compared with those of conventionally produced components B consisting of a red brass alloy, the conventional red brass alloy having the following fractions of alloying components in wt. %:

-   Zn: 5.5% -   Sn: 4.5% -   Pb: 3% -   Ni: 0.5% -   remainder copper.

In addition, FIG. 1 also shows the limit according to the German Drinking Water Ordinance (TrinkwV) by a dashed line and the parameter value W (15) to be adhered to in the migration tests is shown as a continuous line. The parameter value W (15) is the value which must be adhered to in order to avoid the value of the Drinking Water Ordinance being exceeded when using the tested components. This parameter value W (15) is obtained from the product of the limit of the Drinking Water Ordinance and the ratio of the form factors A and B. The factor A is obtained according to DIN 50 931-1 from the ratio of the water-contacted surface of the material to the water-contacted surface of the entire test section. The form factor B is a normalisation factor according to DIN 50 930-6 which takes into account the type of components.

As can be seen, the amount of lead released from the red brass components B decreases almost exponentially from a very high value higher than 50 μg/l within the first four weeks of the test to a value barely above the limit of the Drinking Water Ordinance of 10 μg/l after 12 to 26 weeks of testing. This clear exceeding of the permissible limit can be attributed to the fact that at the beginning of the tests, lead which has reached the surfaces of the tested pipes due to machining migrates into the drinking water. After the first few weeks, the lead near the surface has almost completely migrated into the drinking water and the amount of lead released remains approximately constant.

The component A according to the invention however releases virtually no lead to the drinking water. Even an elevated value at the beginning of the tests cannot be identified. Since the measured values are at the limit of the resolution of the measurement analysis, the measurement fluctuations are attributed to the measurement accuracy of the measuring apparatus. However, the measured values substantially remain significantly below the limit of the Drinking Water Ordinance of 10 μg/l.

The same applies to the behaviour of the nickel release which is also shown measured over 26 weeks in the diagram in FIG. 2. The time behaviour of the quantities of nickel released by the conventional red brass component B shows a typical profile. The amount of nickel released initially exceeds the limit of the German Drinking Water Ordinance after about 9 weeks, before falling after a maximum in the 18^(th) week of testing towards the limit of the Drinking Water Ordinance. The increase in the nickel concentrations in the drinking water from the red brass components B cannot be explained precisely so far. However, the increase is reproducible and the limit of the German Drinking Water Ordinance fixed at about 20 μg/l, likewise shown as a dashed line, is also reproducibly exceeded.

In comparison, the nickel-free component A according to the invention releases no appreciable nickel ions to the drinking water. The measured value of about 2 μg/l also lies within the range of resolution of the measuring equipment used for the analysis.

FIG. 3 again shows the amount of copper released to the drinking water from the components A according to the invention and the red brass components B. Both components show an increase up to the eighteenth week of testing. The measured quantities of released copper then decrease again for both alloys. The limit of the Drinking Water Ordinance for copper is 2000 μg/l. The parameter value W (15) allocated for adhering to the Drinking Water Ordinance is about 3000 μg/l. This limit is likewise not exceeded by the conventional component B with a maximum of 2600 μg/l measured in the eighteenth week, as in the case of the component A according to the invention. For this component the maximum is about 2100 μg/l and is therefore about 20% lower than the maximum for the red brass alloy B. After 26 weeks the amount of copper released decreases again for both alloys. In comparison however, it is noticeable that the components according to the invention release about 500μg/l or about 20-25% less copper ions to the drinking water than conventional components.

Finally FIG. 4 shows the amount of zinc released to the drinking water by the components. There is currently no limit for the release of zinc in the Drinking Water Ordinance. However, the component A according to the invention also differ significantly from the conventional red brass component B in the migration of zinc. Whereas as the component A according to the invention releases a maximum of 100 μg/l of zinc to the drinking water by migration, the zinc release of the conventional red brass component B is more than four times this value at its maximum.

As a result, the test measurements shown in FIGS. 1 to 4 have shown that the migration of undesirable ions into the drinking water can generally be reduced by the components according to the invention. The very good results are attributed to a combination of the migration-inhibiting property of the copper alloy used, but in particular to the method of producing the components according to the invention which results in a denser structure. In particular, the low release of lead ions and nickel ions to the drinking water ensures that the components according to the invention can also be used below more stringent limits with regard to the content of metal ions in drinking water.

FIGS. 5 a to 5 d show typical exemplary embodiments of components for media- or drinking-water-carrying works, fittings, valves and pipes. FIG. 5 a shows a valve housing made from a copper alloy according to the invention which was produced, for example, from a continuously cast rod by extrusion of a thick-walled tube or a solid rod followed by hot pressing or die forging. As a result of the good formability of the alloy according to the invention, good yields can be achieved during production even with correspondingly complex components such as the valve housing shown in FIG. 5 a, for example. The good machinability of the components ensures that components produced by the aforesaid method can be simply machined.

FIG. 5 b shows a simple end cap 2 which has so far mostly been made of pure copper because of the deep drawing process required. With the method according to the invention, the end cap 2 can made from a copper alloy in the same way as the other components of media-carrying works since the end cap 2 can be produced from hot- and/or cold rolled sheet according to the invention by deep drawing. An O ring groove 3 can then be inserted in the end cap 2 by a further cold forming step, for example, mechanical expanding.

FIG. 5 c is a perspective view showing a bent pipe 4 with an overbend 5 and connecting ends 6 on both sides. The pipe 4 has been made from a longitudinally welded pipe produced from a cold- and/or hot-rolled sheet according to the invention or from a cold-drawn pipe. By using cold and/or hot rolling steps during the production of components, the economically more cost-effective method for producing the pipes can be selected according to the available starting material, for example, thick-walled tube or sheet. The overbend 5 is produced by bending the pipe 4. The connecting pieces 6 are preferably produced before the bending either by a simple upsetting and expanding step or inserted into the pipe 4 using an IHU method.

The T-piece 7 shown in perspective view in FIG. 5 d is another typical component for media- or drinking-water carrying works which has so far mostly been made of a red brass alloy. The T-piece 7 also has connecting pieces with O ring grooves 3 at both ends of the crossbar of the T, which are either produced by a subsequent expanding process or during the manufacture of the T-piece 7 by internal high-pressure forming. A cold-drawn pipe is usually cut to length and formed in a tool by internal high-pressure forming after any intermediate annealing. The thread 8 can be incorporated by rolling, for example, in the T-piece blank thus produced.

The roof or drainage gutters not shown in the figures can be produced according to the next exemplary embodiment of the method according to the invention from hot- and/or cold-rolled sheets consisting of the aforementioned copped alloy by simple bending and/or flanging.

As has already been explained, the components, fittings, valves, pipes, press connectors, roof or drainage gutters can be produced from a low-migration copper alloy particularly cost-effectively and therefore economically using the method of manufacture according to the invention. 

1. A method for producing components, media-or drinking-water carrying works, in particular fittings, valves, pipes, press connectors, roof or drainage gutters, characterised in that an ingot or a rod is continuously cast from a copper alloy, wherein the copper alloy has the following alloying components in wt. %: 2%≦Si≦4.5%, 1%≦Zn≦17%, 0.05%≦Mn≦0.6%, unavoidable accompanying elements to a maximum of 0.5% in total, preferably to a maximum of 0.3% in total, the remainder copper and the ingot or the rod for producing the component is subjected at least to one cold and/or hot forming process.
 2. The method according to claim 1, wherein the alloying component Zn has the following fraction in wt. %: 5%≦Zn≦15%.
 3. The method according to claim 1, wherein the alloying component Si has the following fraction in wt. %: 2.8%≦Si≦4%.
 4. The method according to claim 1, wherein the alloying component Mn has the following fraction in wt. %: 0.2%≦Mn≦0.6%.
 5. The method according to claim 1, wherein the copper alloy contains no nickel and/or lead.
 6. The method according to claim 1, wherein the copper alloy has a copper content of at least 80 wt. %.
 7. The method according to claim 1, wherein a thick-walled tube or a solid rod is produced from the ingot or the rod using extrusion.
 8. The method according to claim 7, wherein the thick-walled tube is cold drawn.
 9. The method according to claim 8, wherein the cold-drawn tube is formed by an internal high-pressure (IHU) method.
 10. The method according to one of claims 8, wherein the cold-drawn tube or the IHU-formed tube is subjected in at least one further forming step to bending, expanding, reducing, rolling, thickening, flanging and/or further IHU forming steps with or without intermediate annealing between individual forming steps.
 11. The method according to claim 7, wherein the thick-walled tube or the solid rod is at least hot-pressed or die forged in a plurality of steps.
 12. The method for producing components, media- or drinking-water carrying works, in particular fittings, valves or pipes according to claim 1, wherein after the continuous casting, the ingot is hot- or cold-rolled to produce sheets with or without intermediate annealing and the components are produced from the sheets by further cold and/or hot forming.
 13. The method according to claim 12, wherein a longitudinally welded tube is produced from the cold- or hot-rolled sheets.
 14. The method according to any one of claims 12, wherein the sheets or the longitudinally welded tube is subjected to deep drawing.
 15. Components for media- or drinking-water carrying works, in particular fittings, valves, pipes, press connectors, roof or drainage gutters produced by a method according to claim
 1. 